(Adapted from the investigator's specific aims) The specific aims of this revised application are: 1) Isolate full length mucin cDNAs from rat and human airway libraries; from these determine the primary structure of mucin core protein in both species. 2) Using the rat mucin cDNA, isolate the cognate gene from a rat genomic library and identify upstream (or other) regulatory elements using transfection analysis of deletion mutants. 3) Determine the extent to which these regulatory elements bind nuclear proteins using mobility shift and dNase I protection assays and 4) Establish a rat model of respiratory mucin overproduction and determine whether transcriptional control of mucin biosynthesis is upregulated using a rat mucin cDNA in northern hybridization and nuclear run-on assays.